Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 112116

Area Forecast Discussion
National Weather Service Seattle WA
216 PM PDT Tue Aug 11 2020

.SYNOPSIS...Clouds and sunshine through Wednesday as an upper
level trough slides north of the area. An upper ridge builds into
the Pacific Northwest late Thursday with temperatures warming
through the weekend with dry weather.


.SHORT TERM /TONIGHT THROUGH FRIDAY/...Mostly sunny skies across
the area this afternoon with increasing high clouds as a weak
shortwave approaches. Seasonable temperatures today with upper 60s
to mid 70s. Clouds will increase into this evening as the
shortwave slides through, though most areas will be dry. Hi-res
guidance highlights the possibility of at least some convergence
near the central Puget Sound so have at least a slight chance of
precip in this area, though may just be increased low- mid clouds
and be dry. Clouds will be around into Wednesday morning with some
clearing in the afternoon. Highs Wednesday will be a bit cooler
in the upper 60s to low 70s.

The upper trough north of the area will slide east Thursday
morning as an upper ridge builds into the Pacific Northwest.
Any morning clouds will clear quicker for more sunshine in the
afternoon with highs into the mid 70s.

The upper ridge will impact the Pacific Northwest Friday and
through the weekend for dry weather. Temperatures will warm Friday
into the 70s and low 80s across the area. JD

.LONG TERM /SATURDAY THROUGH TUESDAY/...The upper ridge will build
even more into Western Washington Saturday and Sunday.
Temperatures will warm Saturday into the 80s across much of the
Southwest Interior into the Puget Sound. Sunday may be the warmest
day of the stretch, though there is some uncertainty as to how
long the ridge is over the Pacific Northwest with a trough well
offshore. Highs on Sunday will be in 80s across most of the area
with 90s at least across the Southwest Interior and into the
southern Puget Sound, though will have to monitor if it is even a
few degrees warmer. Guidance highlights a weak shortwave riding
the ridge late Sunday night into Monday with just a slight chance
for precipitation with temperatures dropping a few degrees. There
is some uncertainty whether the ridge builds for Tuesday, though
temperatures are expected to be above average for the area. JD


.AVIATION...Continued clearing this afternoon for all TAF locations.
An upper level trough will be passing through the area tonight. This
will bring gusty winds in excess of 15 knots at KPWT and KBLI.
Beginning around 0400 UTC the onshore flow will start to bring
clouds into KHQM, followed by KPWT a few hours later. This marine
push is not expected to effect the more inland airports until around
0800 UTC. Once clouds have moved into the area MVFR and IFR
conditions are expected. VFR conditions are expected to return by
around 1500 UTC Wednesday morning for much of the area. The clearing
will be delayed until the afternoon for coast.

KSEA...VFR conditions are to remain for the rest of the afternoon.
Winds will remain westerly and decreasing to around 5 knots this
evening and into tonight. After midnight the marine push will force
winds to become Southerly and start to bring in clouds. MVFR
conditions are possible by Wednesday morning. Clearing is expected
to begin around 1500 UTC and sky conditions will slowly improve to
VFR through Wednesday afternoon.


.MARINE...Onshore flow will persist through Thursday before a ridge
of high pressure builds over the area. Strong pushes are likely
through the Strait each afternoon and evening through Thursday. Gale
force winds are expected for the central and eastern Strait starting
this evening and lasting into Wednesday morning. Strong winds may
bleed over into Admiralty Inlet and northern Inland waters, a small
craft advisory will be in effect for those areas. Winds and swell
across the coastal waters will gradually diminish below criteria by
Wednesday morning. Winds are expected to decrease through Wednesday
afternoon, and begin to pick back up starting at 0000 UTC Thursday.
Models are suggesting that the marine push through the Strait will
not be as strong, but a small craft advisory is not out of the
question for Wednesday into Thursday.



.FIRE WEATHER...Onshore flow with cooler temperatures through
Thursday with no major fire weather concerns. An upper ridge
builds into the area late week through the weekend. Dry and
unstable conditions are possible, mainly for Sunday, with rather
low RHs and mid level haines indices of 6. This will be monitored
through the week. JD


.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.


PZ...Small Craft Advisory until 5 AM PDT Wednesday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

     Gale Warning until 3 AM PDT Wednesday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
     Juan De Fuca.

     Small Craft Advisory until 3 AM PDT Wednesday for Admiralty
     Inlet-Northern Inland Waters Including The San Juan Islands.


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